Ginger Pistachio Float, made with an easy ginger syrup. (Deb Lindsey /For The Washington Post)

The Tootsie ice cream float, made with sour cherry syrup. (Deb Lindsey /For The Washington Post)

Like a seven-layer dip after five minutes with a chip-wielding mob, the ice cream float is at its best when it looks a mess. That chilled scoop needs to meld into what’s in the glass, creating a foamy head, a likely puddle below and the kind of creamy drink that was intended when the float, a.k.a. ice cream soda, was invented in the 1870s.

You might think a written recipe amounts to overkill. What does it take beyond ice cream, soda, straw and spoon? Well, a little extra attention to ingredients pays off.

Stirring flavored syrup into plain seltzer makes for a soda that’s less sweet than what you can find on the soft drinks aisle, and that custom blending comes in handy for a tasteful balance once the ice cream goes in. There are plenty of syrups on the market, but for some reason they come in 750-milliliter bottles, which is way more than you need for even a party-size batch o’ floats. It’s easy enough to make your own syrups by simply boiling down a pure fruit juice or infusing a classic sugar-and-water mix.

When you go the boozy route, keep in mind that a strong-tasting concoction will be mellowed considerably. Consult a guide like “The Flavor Bible” to experiment with flavor affinities and complementary notes in spirits and bitters.

The scoop you choose matters, too, of course. Gelato will melt faster than premium ice cream, but it has a bit less fat and may result in a different mouth feel. Sorbets, which are typically nondairy, won’t yield a surface that’s quite as foamy. You might not want to choose ice cream with chunks that would get stuck in a straw. But do venture beyond simple vanilla and chocolate.

Finally, there’s the presentation. The folks behind the Brooklyn Farmacy and Soda Fountain recommend the made-to-order technique used in their Carroll Gardens neighborhood shop: Stir the syrup and seltzer mixture in each tall glass, leaving a generous amount of head space. Perch the scoop of ice cream on the rim, then fill with more seltzer just until the level of liquid meets the scoop and bubbles form. Then, blending and melting will ensue with some control, as you drink and stir.

Sure enough, some ice cream will run down the side of the glass, and soon the scoop will fall in and bob on the surface. That’s why you serve an ice cream float on a saucer plate.

Start with this batch of floats for inspiration, and invest in a few long spoons.

Ginger Pistachio Float, pictured above, at left. We really liked what the ginger-forward syrup brings to this party. It and the seltzer create a soda that’s less sweet than ginger ale, and creamy-cool.

The Tootsie, pictured above, at right. We’re making a DIY exception here. The sour cherry syrup that’s available year-round in Eastern European and Russian markets makes for a winning soda flavor — nice and tart — and we bet you’ll find other uses for it once it’s in your pantry.

The Purple Cow. (Deb Lindsey /For The Washington Post)

Malted Root Beer Float. (Deb Lindsey /For The Washington Post)

Purple Cow. Concord grapes are a fall crop, so we cooked down 100 percent Concord grape juice to create a homemade syrup here.

Malted Root Beer Float. The addition of malt syrup (store-bought) is subtle, but it makes for a creamy-dreamy flavor.

Boozy Orange Pomegranate Float. (Deb Lindsey /For The Washington Post)

Prosecco Sabayon Float. (Deb Lindsey /For The Washington Post)

Boozy Orange Pomegranate Float. Gin, orange liqueur and pomegranate syrup make a potent mix — so don’t taste this drink until the seltzer and gelato are stirred in. The overall effect heads into Creamsicle territory.

Prosecco Frozen Sabayon Float. Inspired by David Lebovitz’s no-churn Frozen Sabayon, we plopped a few small scoops into a flute and filled with prosecco until the bubbles happened on top.